1. Field of the Invention
The present invention relates to use of compressed image data to address a look-up table, and particularly concerns utilizing compressed RGB color image data to index a look-up table for providing corresponding CMYK data.
2. Description of the Related Art
Recently, 32-bit printer drivers have become available, primarily because 32-bit printer drivers can take advantage of certain features that are available for 32-bit code, but not for 16-bit code. However, for historical reasons many operating systems, such as Windows 95.TM., are designed to communicate only with 16-bit printer drivers. Therefore, many of the new 32-bit printer drivers actually include both a 16-bit portion, which interfaces with the operating system, as well as a 32-bit portion in which most of the actual processing is performed.
Specifically, the operating system is typically configured to receive RGB (red, green blue) print data from an application program and to provide the RGB data to a 16-bit printer driver. Accordingly, the printer driver uses its 16-bit portion to receive the RGB data. Typically, the 16-bit portion of the driver then immediately either spools the RGB data to a spool file for use by the 32-bit portion or else directly transfers the data to the 32-bit portion of the driver.
Upon receipt of the RGB data, or access to the spool file in the event of spooling, the 32-bit portion ordinarily first performs color matching. Color matching involves converting the input RGB data into CMYK (cyan, magenta, yellow and black) data and frequently includes performing data corrections based on the source of the RGB data. Thereafter, the 32-bit portion of the printer driver performs further additional processing in order to generate data which can be used by the printer.
However, several problems exist with the foregoing conventional configuration. First, the transfer time from the 16-bit portion of the printer driver to the 32-bit portion can be significant, particularly when the 16-bit portion of the driver spools the print data to a spool file. In this regard, the RGB data are usually represented by 8 bits per pixel per color. Accordingly, a single 81/2'.times.11' page can require the 16-bit portion to spool to disk, and then the 32-bit portion to read from the disk, 33 megabytes of data. Correspondingly, 33 megabytes of disk space generally must be set aside per spooled page.
Moreover, as noted above, upon obtaining the RGB data the 32-bit portion of the conventional printer driver typically performs color matching, requiring additional processing time. Even if caching is used, this step still can consume significant processing time.